1. Field of the Invention
This invention relates to an automatic focusing device for cameras, microscopes or the like which can automatically adjust the focal point of a lens.
2. Description of the Prior Art
Heretofore, various automatic focusing devices for cameras, microscopes or the like have been proposed. In these conventional devices, all or part of an image formed on a screen by a lens is decomposed into a number of picture elements and informations such as brightness of these picture elements are used so as to adjust the focal point of the lens. As a result, the conventional devices comprise means for decomposing the image into the picture elements and means for processing informations obtained by each picture element. These process operations are too complex or too simple in contents to precisely adjust the focal point of the lens. For example, in one of the conventional devices, use is made of analog, digital or hybrid operations which are too complex to precisely adjust the focal point of the lens. In the other conventional deivce, the process operations are too simple to precisely adjust the focal point of the lens. In a further conventional device, the process operations are effected on the basis of Fourier transformation or variance, so that such conventional device is comlex in construction. As can be seen from the above, in the case of obtaining informations required for focusing the lens on the basis of the picture elements, a problem arises as to how to effect the process operation of the informations obtained from each picture element for the purpose of providing an image forming signal.